This invention relates to a method of cleaning the inner wall of a pipe.
Scale or slag can deposit on the inner wall of a pipe for supplying water, pertroleum or various types of gases and can eventually reduce the effective cross sectional area of the pipe and thus impede the flow of fluids therethrough. For this reason, the inner wall surface of the pipe is cleaned periodically to remove the scale.
To clean a pipe of the type described, a sweeper (also referred to as a "pig") made of synthetic resin and having a conical portion at its forward end is inserted into the pipe while being elastically deformed, hydraulic pressure is applied to the rearward end of the sweeper within the pipe, and the scale on the inner wall of the pipe is scraped off by the sweeper while the sweeper is advanced through the pipe by a difference in pressure between the forward and rearward ends of the sweeper. The scraping off of the scale is actually performed by the heads of a number of metal pins driven in toward the center of the sweeper from the outer peripheral surface thereof. The heads of these pins advance together with the sweeper while being brought into pressured contact with the inner wall of the pipe and strike the scale to remove the same from the inner wall. The pins are made of a material not as hard as that of the pipe and somewhat harder than that of the scale or slag to be scraped off from the inner wall of the pipe.
Pins of this type and a sweeper equipped with the pins have already been proposed by the inventor in Japanese Patent Publication (KOKOKU) No. 58-36634 and Japanese Utility Model Publication (KOKOKU) No. 58-45831.
The conventional sweeper described above is capable of cleaning a pipe efficiently providing that the diameter of the pipe to be cleaned is constant over the entire length of the pipe. However, the conventional sweeper is not suitable for a pipe having an irregular diameter, namely a pipe whose diameter differs along the length of the pipe. Specifically, at a portion of such a pipe having a larger diameter, the heads of the pins driven into the sweeper will not make good pressured contact with the inner wall of the pipe. At portions where the diameter is small, the sweeper will not be able to pass through the pipe.